Changes in neuromuscular junction endplate current time constants produced by sulfhydryl reagents.

The acetylcholine receptor is a protein that contains certain critical disulfide bonds. Experiments were designed to determine the role such bonds might play in the physiological activity of the receptor. Modification of the receptor with sodium bisulfite and diamide produced an increase in the time constants of the miniature endplate current without changes in the single-channel properties of the receptor. Controls were done to determine that this change in the miniature endplate current was not due to an effect on acetylcholinesterase at the endplate. These data are interpreted to mean that the reagents increase the time acetylcholine is bound to the receptor before the channel opens and is most probably due to a change in receptor affinity brought about by chemical modification of the receptor protein.